Post Multiple items / an array with Express & Postman

Question

unfortunately I have problems to post an Array to my Express Server. I post an item and if it exists in the db it will be deleted.

My code:

item.routes.js

module.exports = app => {
    
  const item = require("../controllers/item.controller.js");

  app.post("/itemr", item.IsReserved);
};

item.controller.js

const Item = require("../models/item.model.js");

exports.IsReserved = (req, res) => {
  // Validate request
  if (!req.body) {
    res.status(400).send({
      message: "Content can not be empty!"
    });
  }

  const item = new Item({
    itemId: req.body.assetId,
    botId: req.body.botId,
  });

  Item.IsReserved(item, (err, data) => {
    if (err)
      res.status(500).send({
        message:
          err.message || "Some error occurred while creating the Item(db)."
      });
    else res.send(data);
  });
};

item.model.js

const sql = require("./db.js");

Item.IsReserved = (RItem, result) => {
    sql.query(`SELECT * FROM ReservedItems WHERE itemId = "${RItem.itemId}"`, (err, res) => {
        if(res.length){
            sql.query(`DELETE FROM ReservedItems WHERE itemId = "${RItem.itemId}"`, (err, res) => {
                if (err) {
                    console.log("error: ", err);
                    result(err, null);
                    return;
                }
                result(null, { id: res.insertId, ...RItem });
            });
        }
        else{
            result(null, { message: "nothing to do"});
        }
    });
};


module.exports = Item;

A single item works great with a post like this:

{
   "assetId" : 3,
   "botId" : "1"
}

but if I want to insert multiple items like this:

[
    {
        "assetId" : 3,
        "botId" : "1"
        },
        {
        "assetId" : 4,
        "botId" : "1"
    }
]

The result from this is "nothing to do"...

My sql log shows: Query SELECT * FROM ReservedItems WHERE itemId = "undefined"

I saw another post here which had a similar problem, but I don't know how to implement something like ".create()" into my code to recognize multiple items.

I would be very thankful for every answer!

Does this answer your question? node.js request POST array "first argument must be string or buffer" — BadPiggie
– BadPiggie, Commented Nov 5, 2021 at 13:07

TLd · Accepted Answer · 2021-11-05 13:29:11Z

There are many approaches to fix your problem :)

First of all in your controller, this is not possible anymore as you send an array of items in your request payload. So you need to define an array aswell :

  const items = req.body.map((item) => new Item({
    itemId: item.assetId,
    botId: item.botId,
  });

As your method IsReserved handles only 1 item, you can use Promise.all to apply modifications. Something like this :

Promise.all( items.map( (item) => Item.isReserved(item)))
.then( (result) => ...do something here)
.catch( (error) => ...do something else here)

Another approach could be to change the SQL statement and use WHERE IN

SELECT * FROM ReservedItems WHERE itemId IN (itemid1, itemid2...)

This will get you an array of items that you can then delete the same way. It seems better in terms of performance.

I also recommand to use async/await syntax as it's way easier to read code containing promises

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